This invention relates to a sampling system comprising a sampling circuit having a signal input for supplying a signal to be sampled and having a first and a second pulse input for respectively supplying a first sampling pulse and a second sampling pulse whose phase is opposite to that of the first sampling pulse, and further comprising a pulse generation circuit, coupled to the sampling circuit via the pulse inputs, for generating the first and second sampling pulse.
The invention further relates to a pulse generation circuit and a sampling circuit suitable for use in such a sampling system.
The invention also relates to an oscilloscope equipped with such a sampling system.
Such a sampling system is known from the U.S. Pat. No. 3,241,076. In that case, as can be seen in FIG. 3, the pulse generation circuit having a mutually twisted two-wire signal line ("twisted pair") is connected to the sampling circuit. Furthermore, capacitors are used as charge storage components. In practice, the capacitors will have tolerances and will never be completely identical to each other. As a consequence of this design, imbalances will occur in the system, further intensified by imbalances in the pulse generation circuit itself. Temperature variations may also affect the capacitors. If such a sampling system is used, for example, in an oscilloscope with which it is required to measure signals of small amplitude, these imbalances may have a considerable effect. If there is, for example, 1% imbalance and if the input signal to be measured has an amplitude of 1 mV, an unbalanced pulse signal which itself has an amplitude of, for example, 3 V, will contribute 30 mV, a signal which is large compared with the input signal to be measured.